1. Field of the Invention
The present invention relates to an improved substrate cleaning technique, and more particularly to a technique for enabling both an ability of removing a foreign matter which is on a surface of a substrate and an ability of discharging a removed foreign matter from the surface of the substrate.
2. Description of the Prior Art
As well known, surface processing using various types of processing liquid is performed on a substrate such as a glass substrate for a liquid crystal display apparatus and a semiconductor wafer. Following such processing, it is necessary to remove remaining processing liquid from a substrate. It is also important to remove particles which are adhered to the surface of the substrate. For removal of such a foreign matter, the substrate is subjected to a cleaning process. Cleaning methods are generally divided into chemical cleaning and physical cleaning.
Chemical cleaning includes one using pure water, one using neutral or alkaline cleaning liquid, one using ozone water which is obtained by solving ozone in cleaning liquid, etc. Such chemical cleaning, being based on chemical solving, is effective for removal of a relatively fine foreign matter and a foreign matter which is chemically bonded to a substrate, but is not effective for removal of a relatively large foreign matter. For this reason, physical cleaning is often performed in addition to chemical cleaning.
Meanwhile, there are various types of methods of physical cleaning. As each of the methods has both advantages and disadvantages, sufficient physical cleaning is difficult with one method alone. Hence, in many cases, more than one physical cleaning method are combined to achieve the desired level of cleaning.
Under the circumstance, parallel use of a plurality of physical cleaning methods within one apparatus has been proposed. For example, Japanese Patent Laid Open Official Gazette No. 7-86218 discloses an apparatus which simultaneously performs both a brush-cleaning method with a rotating brush and an ultrasonic cleaning method with ultrasonically vibrated liquid.
Execution of a plurality of cleaning methods within one apparatus as disclosed by Japanese Patent Laid Open Official Gazette No. 7-86218 is related to a time which is needed for cleaning. In other words, as substrates have become larger in recent years, the demand for a shortened cleaning time has been mounting. If cleaning apparatuses of different methods are arranged linearly and cleaning is performed serially by these cleaning apparatuses, the cleaning time which is available for each cleaning apparatus is shortened and therefore its cleaning ability is reduced.
However, such an apparatus for a brush-cleaning method as that disclosed by Japanese Patent Laid Open Official Gazette No. 7-86218 has another problem. That is, although a brush-cleaning method has an excellent ability to remove a foreign matter, as being physical cleaning which requires a physical contact, the method gives damage such as a flaw to a surface of a substrate.